Laser range finders for determining the range to distant objects are well known. Such range finders find application in a variety of fields such as surveying, collision avoidance, and targeting.
Such laser range finders comprise a laser receiver and a coaxially mounted laser transmitter which is much smaller than the laser receiver. Such coaxial mounting of the laser receiver and laser transmitter results in operation of both devices along a common optical axis and thus both enhances the accuracy of the range finder and facilitates packaging thereof within a smaller volume. As those skilled in the art will appreciate, the farther away from the receiver that the transmitter is mounted, i.e., the more the devices deviate from having a common optical axis the less accurate the laser range finder tends to be.
It is generally desirable to package such laser range finders as efficiently as possible, since they are typically utilized upon vehicles, wherein space is typically at a premium. For example, in collision avoidance applications the laser range finder is typically disposed within an automobile or aircraft, wherein little room is available therefor.
However, one problem commonly associated with such contemporary laser range finders is that of insufficient power output from the laser transmitter. Insufficient power output is of particular concern, especially when the laser beam must be transmitted through an attenuating medium such as rain, fog, snow, water, dust, etc.
When the laser range finder output beam must be transmitted through such an attenuating medium, it is desirable to increase the output power thereof, so as to compensate for attenuation to both the output beam and the reflected beam.
However, the provision of additional output power is in conflict with the packaging requirements which dictate that the laser transmitters be located proximate the laser receiver, such that a common optical axis is defined therefore and also in order to maintain packaging efficiency.
Prior art attempts to enhance the output power of such laser range finders include the use of optical fibers and polarizing beam combiners. However, the use of such optical elements inherently introduces alignment problems and reduces the overall efficiency of the laser transmitting system. It also undesirably increases the complexity and cost of the system.
As such, it is beneficial to provide a means for increasing the output power of the laser transmitter of a laser range finder or the like, so as to facilitate use thereof in adverse conditions.